Wound healing, or wound repair, is the body's natural process of regenerating dermal and epidermal tissue. After a wound occurs, a set of complex biochemical events takes place in a closely orchestrated cascade to repair the damage. These events overlap in time and may be artificially categorized into separate steps: the inflammatory, proliferative, and maturation and remodeling phases. In the inflammatory phase, bacteria and debris are phagocytized and removed, and factors are released that cause the migration and division of cells involved in the proliferative phase. The proliferative phase is characterized by angiogenesis (formation of new blood vessels from endothelial cells), fibroplasia, collagen deposition, granulation tissue formation, epithelialization, and wound contraction. In the maturation and remodeling phase, collagen is remodeled and realigned along tension lines and cells that are no longer needed are removed by apoptosis.
There are two types of wounds, open and closed. Open wounds are classified according to the object that caused the wound. For example, incisions or incised wounds (including surgical wounds) are caused by a clean, sharp-edged object such as a knife, a razor or a glass splinter. Lacerations are irregular wounds caused by a blunt impact to soft tissue which lies over hard tissue (e.g., laceration of the skin covering the skull) or tearing of skin and other tissues such as caused by childbirth. Abrasions or grazes are superficial wounds in which the topmost layer of the skin (the epidermis) is scraped off. Puncture wounds are caused by an object puncturing the skin, such as a nail or needle. Penetration wounds are caused by an object such as a knife entering the body. Gunshot wounds are caused by a bullet or similar projectile driving into (e.g., entry wound) and/or through the body (e.g., exit wound). In a medical context, all stab wounds and gunshot wounds are considered major wounds. Open wounds also include burn wounds induced by thermal, chemical, or electrical injury.
Closed wounds include contusions (more commonly known as a bruise, caused by blunt force trauma that damages tissue under the skin), hematoma (also called a blood tumor, caused by damage to a blood vessel that in turn causes blood to collect under the skin), and crushing injuries (caused by a great or extreme amount of force applied over a long period of time).
Chronic wounds are wounds that have failed to proceed through an orderly and timely series of events to produce a durable structural, functional, and cosmetic closure. Many chronic wounds are cutaneous wounds or ulcers, caused by factors such as diabetes, venous stasis, arterial insufficiency, or pressure. Certain cutaneous wounds are burn wounds, induced by thermal, chemical, or electrical injury. Chronic wounds are the source of significant pain and suffering. If left without treatment they can cause life threatening complications, reduce the rate of recovery or worsen other health conditions. Intensive and effective treatment can help restore skin integrity, and avoid unwanted health problems. While these wounds are inflicted by different causes, the wound healing process and the wound treatment strategies are similar in many respects.
Bed sore are one type of pressure ulcers which may significantly reduce the quality of life and negatively affect general prognosis. Bed sores are localized areas of skin injury that develop when soft tissue is compressed between a bony prominence and an hard surface for a long time. Bed sores usually develop from laying or sitting for a prolonged period without changing the body posture. For those who are bed-bound, pressure sores are most likely to form on or around the heels, the hip-bone, and the lower back or tailbone. Pressure ulcers may also develop in a variety of other areas, including the spine, ankles, knees shoulders, and head, depending upon the position of the patient. If left without treatment, bedsores may degenerate to the stage of decay of epithelial tissue, with inflammation, bacterial infection and other serious complications. The body's response to the infection often results in fever, shaking chills, changes in mental status, rapid pulse, and respiratory rate.
Temporary dressings, including interactive temporary dressings, are intended to provide supportive care until definitive closure can be accomplished. Temporary dressings are expected to function as a barrier, much like human skin. Available wound dressings are effective to a degree, but have significant shortcomings, such as high frequency of dressing changes, wound drying or dressing adherence, high treatment costs, development of a foreign body reaction, and a low rate of improvement, especially in elderly patients. The foreign body reaction begins as wound healing, including accumulation of exudate at the site of injury, infiltration of inflammatory cells to debride the area, and the formation of granulation tissue. However, the persistent presence of a foreign body can inhibit full healing. Rather than the resorption and reconstruction that occurs in wound healing, the foreign body reaction is characterized by the formation of foreign body giant cells, encapsulation of the foreign object, and chronic inflammation. Encapsulation refers to the firm, generally avascular collagen shell deposited around a foreign body, effectively isolating it from the host tissues. This response was developed as a protective measure. The foreign body reaction can lead to chronic pain.
Healing time of a chronic wound can range from a few weeks to a year, depending on the size and type of wound. Wound treatment involves many direct and indirect costs. According to the International Committee on Wound Management (ICWM), wound dressings comprise only 10 percent to 15 percent of the total direct treatment cost (International Committee on Wound Management, 1994, Wounds 6(3): 94-100). In contrast, a significant percentage of total cost is attributed to care provider salary and staff expenses (International Committee on Wound Management, 1994, Wounds 6(3): 94-100).
There is a need in the art for wound dressings that do not induce foreign body reactions or do so at a lower rate than traditional wound dressings. Such wound dressings would need to be changed on a less frequent basis and reduce healing time to closure, and thus may translate into more effective therapy for the patient and a reduced cost of care.